add tests

src/spatialdata/_core/spatialdata.py

@@ -1495,7 +1495,8 @@ def write_channel_names(self, element_name: str) -> None:
         Parameters
         ----------
         element_name
-            The name of the element to write. If None, write the channel names of all image elements.
+            The name of the element to write the channel names of. If None, write the channel names of all image
+            elements.
         """
         from spatialdata._core._elements import Elements
 
@@ -1514,15 +1515,17 @@ def write_channel_names(self, element_name: str) -> None:
 
         element_type, element = validation_result
 
-        # Mypy does not understand that path is not None so we have a conditional
-        if self.path is not None:
+        # Mypy does not understand that path is not None so we have the check in the conditional
+        if element_type == "images" and self.path is not None:
             _, _, element_group = self._get_groups_for_element(
                 zarr_path=Path(self.path), element_type=element_type, element_name=element_name
             )
 
             from spatialdata._io._utils import overwrite_channel_names
 
             overwrite_channel_names(element_group, element)
+        else:
+            raise ValueError(f"Can't set channel names for element of type '{element_type}'.")
 
     def write_transformations(self, element_name: str | None = None) -> None:
         """

tests/io/test_metadata.py

@@ -111,11 +111,22 @@ def test_save_transformations_incremental(element_name, full_sdata, caplog):
 
 
 # test io for channel names
-@pytest.mark.skip(reason="Not implemented yet")
 def test_save_channel_names_incremental(images: SpatialData) -> None:
-    # note: the non-incremental IO for channel names is already covered in TestReadWrite.test_images(), so here we
-    # only test the incremental IO
-    pass
+    with tempfile.TemporaryDirectory() as tmp_dir:
+        f0 = os.path.join(tmp_dir, "sdata.zarr")
+        images.write(f0)
+
+        new_channels = ["first", "second", "third"]
+        images.set_sdata_image_channel_names("image2d", new_channels)
+        images.set_sdata_image_channel_names("image2d_multiscale", new_channels)
+        images.set_sdata_image_channel_names("image3d_numpy", new_channels)
+        images.set_sdata_image_channel_names("image3d_multiscale_numpy", new_channels)
+
+        images = SpatialData.read(f0)
+        assert images["image2d"].coords["c"].data.tolist() == new_channels
+        assert images["image2d_multiscale"]["scale0"]["image"].coords["c"].data.tolist() == new_channels
+        assert images["image3d_numpy"].coords["c"].data.tolist() == new_channels
+        assert images["image3d_multiscale_numpy"]["scale0"]["image"].coords["c"].data.tolist() == new_channels
 
 
 # test io for consolidated metadata